Swimming and pool games can work up quite a thirst. Smoothies are a great, nutritious alternative to sodas and fruit juices. They provide a ton of nutrients and are satisfying (and cold!) on a hot day.
Making smoothies is almost foolproof. A basic smoothie recipe calls for a serving of fruit such as peaches, bananas or strawberries. Use any kind of liquid as a base; water, milk, juice and yogurt all work well. To save time, freeze pre-measured servings of fruit so you can just throw them into the blender. You can also add protein powder or wheat germ to bump up the nutrition for kids who might be finicky eaters.
It's better to make smoothies and serve immediately, but you can make a big pitcher and keep refrigerated until you're ready to drink. The smoothies will keep for a few hours, but stir before you pour. It's a sweet, frozen treat in a glass!